ca. 57:00 -- he talks here about the hidden-bit trick without using that term for it

the hidden-bit trick is akin to the times-4 trick in its purpose, which is to make more efficient use
of the available bits (available bits being a scarce resource, that's a good thing;
it also gives us a great source of quiz questions, which is also a good thing)

the hidden-bit trick is also akin to the times-4 trick in its method, which is to leave out of the
representation those bits whose values we know anyway (2 zeroes on the right in the times-4 trick
and 1 one on the left in the hidden-bit trick)

notice that the designers valued 1 extra bit enough that they went to the trouble of using this trick

Appendix A has a big section of floating-point instructions

these instructions are executed by a separate processor: Coprocessor 1